Year	%
2006	17.9
2007	17.7
2008	17.5
2009	17.3
2010	17.6
2011	17.6
2012	17.6
2013	17.5
2014	17.6
2015	17.4
2016	17.5
2017	17.6
2018	17.7
2019	16.9
2020	17